Increasingly, wells are being drilled to greater and greater depths for the production of oil and natural gas. As a result, alloy compositions used for the manufacture of well tubulars such as casing, tubing and drill pipe, and for the manufacture of downhole devices such as valves, are being subjected to increasingly hostile environments. Serious environmental factors having an adverse effect on such alloy compositions include corrosion, hydrogen embrittlement, and stress corrosion cracking. The most serious of these environmental factors is stress corrosion cracking, which consists of concentrated chemical attack on the material by the environment and which is aggravated by the high temperatures and stresses associated with deep and corrosive wells.
Considerable effort is being expended by the metallurgical industry to develop alloys for use in deep and corrosive wells. The alloys which have been developed are generally hardened or strengthened by cold working, as opposed to being precipitation hardened as are the alloys of the present invention.
Although some of the alloys developed have served the drilling industry with varying degrees of success, there is still a great need in the industry for the development of precipitation hardened alloys having improved strength and resistance to stress corrosion cracking.